You say Iranians can access crypto exchanges and exchange their currency for Bitcoin?
There is a way for them to do those exchanges and transactions. We may not know the actual strategy of how they do it.
But as per checking, coinbase has that.
Convert IRR TOMAN to Bitcoin BTC
You say Iranians can access crypto exchanges and exchange their currency for Bitcoin?
It's possible but the whole details might not be known for most of us if there are exchanges who are particular of not allowing access from that country.
AFAIK, we've got forum members from that country and it's likely that they have access to some exchanges that's accessible to them.